as
this. The substantiation of an ice-cap at the pole will disprove the
first hypothesis; for what we took for ice before alighting may have
been but banks of cloud, since, having been in the plane of the
planet's equator at the time, we had naturally but a very oblique view
of the poles; while the absence of glacial scratches shows, I take it,
that though the axis may have been a good deal more inclined than at
present, it has not, at all events since Jupiter's Palaeozoic period,
been as much so as that of Uranus or Venus. The land on Jupiter,
corresponding to the Laurentian Hills on earth, must even here have
appeared at so remote a period that the first surface it showed must
long since have been worn away, and therefore any impressions it
received have also been erased.

"Comparing this land with the photographs we took from space, I should
say it is the eastern of the two crescent-shaped continents we found
apparently facing each other. Their present form I take to be only the
skeleton outline of what they will be at the next period of Jupiter's
development. They will, I predict, become more like half moons than
crescents, though the profile may be much indented by gulfs and bays,
their superficial area being greatly increased, and the intervening
ocean correspondingly narrowed. We know that North America had a very
different shape during the Cretaceous or even the Middle Tertiary
period from what it has now, and that the Gulf of Mexico extended up
the valley of the Mississippi as far as the Ohio, by the presence of a
great coral reef in the Ohio River near Cincinnati. We know also that
Florida and the Southeastern Atlantic States are a very recent addition
to the continent, while the pampas of the Argentine Republic have, in a
geological sense, but just been upheaved from the sea, by the fact that
the rivers are all on the surface, not having had time to cut down
their channels below the surrounding country. By similar reasoning, we
know that the canon of the Colorado is a very old region, though the
precipitateness of its banks is due to the absence of rain, for a local
water-supply would cut back the banks, having most effect where they
were steepest, since at those points it would move with the greatest
speed. Thus the majestic canon owes its existence to two things: the
length of time the river has been at work, and the fact that the water
flowing through it comes from another region where, of course,